21
Briefly press the volume knob, and filter button simultaneously.
1.
Two LEDs will light up to indicate the output mode.
2.
RCA/XLR output set to fixed mode with volume knob disabled: MQA/DSD light up for 5s.
RCA/XLR output set to variable mode (default) with volume knob enabled: 176.4/768 LEDs light up for 5s.
Note: Headphone output is always variable.